Insect tucked into ordinary banana (8)
I believe the answer is:
plantain
'banana' is the definition.
(plantain is a kind of banana)
'insect tucked into ordinary' is the wordplay.
'insect' becomes 'ant' (ant is a kind of insect).
'tucked into' means one lot of letters goes inside another.
'ordinary' becomes 'plain' (I've seen this before).
'ant' placed inside 'plain' is 'PLANTAIN'.
(Other definitions for plantain that I've seen before include "Green-skinned banana" , "Banana-like fruit" , "Shrub; green banana" , "Large banana - weed" , "Tropical food" .)